packet.c

   1 /*
   2  *
   3  * packet.c
   4  *
   5  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   6  *
   7  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   8  *                    All rights reserved
   9  *
  10  * Created: Sat Mar 18 02:40:40 1995 ylo
  11  *
  12  * This file contains code implementing the packet protocol and communication
  13  * with the other side.  This same code is used both on client and server side.
  14  *
  15  * SSH2 packet format added by Markus Friedl.
  16  *
  17  */
  18
  19 #include "includes.h"
  20 RCSID("$Id$");
  21
  22 #ifdef HAVE_OPENSSL
  23 # include <openssl/bn.h>
  24 # include <openssl/dh.h>
  25 # include <openssl/hmac.h>
  26 #endif /* HAVE_OPENSSL */
  27 #ifdef HAVE_SSL
  28 # include <ssl/bn.h>
  29 # include <ssl/dh.h>
  30 # include <ssl/hmac.h>
  31 #endif /* HAVE_SSL */
  32
  33 #include "xmalloc.h"
  34 #include "buffer.h"
  35 #include "packet.h"
  36 #include "bufaux.h"
  37 #include "ssh.h"
  38 #include "crc32.h"
  39 #include "cipher.h"
  40 #include "getput.h"
  41
  42 #include "compress.h"
  43 #include "deattack.h"
  44 #include "channels.h"
  45
  46 #include "compat.h"
  47 #include "ssh2.h"
  48
  49 #include "buffer.h"
  50 #include "kex.h"
  51 #include "hmac.h"
  52
  53 #ifdef PACKET_DEBUG
  54 #define DBG(x) x
  55 #else
  56 #define DBG(x)
  57 #endif
  58
  59 /*
  60  * This variable contains the file descriptors used for communicating with
  61  * the other side.  connection_in is used for reading; connection_out for
  62  * writing.  These can be the same descriptor, in which case it is assumed to
  63  * be a socket.
  64  */
  65 static int connection_in = -1;
  66 static int connection_out = -1;
  67
  68 /*
  69  * Cipher type.  This value is only used to determine whether to pad the
  70  * packets with zeroes or random data.
  71  */
  72 static int cipher_type = SSH_CIPHER_NONE;
  73
  74 /* Protocol flags for the remote side. */
  75 static unsigned int remote_protocol_flags = 0;
  76
  77 /* Encryption context for receiving data.  This is only used for decryption. */
  78 static CipherContext receive_context;
  79
  80 /* Encryption context for sending data.  This is only used for encryption. */
  81 static CipherContext send_context;
  82
  83 /* Buffer for raw input data from the socket. */
  84 static Buffer input;
  85
  86 /* Buffer for raw output data going to the socket. */
  87 static Buffer output;
  88
  89 /* Buffer for the partial outgoing packet being constructed. */
  90 static Buffer outgoing_packet;
  91
  92 /* Buffer for the incoming packet currently being processed. */
  93 static Buffer incoming_packet;
  94
  95 /* Scratch buffer for packet compression/decompression. */
  96 static Buffer compression_buffer;
  97
  98 /* Flag indicating whether packet compression/decompression is enabled. */
  99 static int packet_compression = 0;
 100
 101 /* default maximum packet size */
 102 int max_packet_size = 32768;
 103
 104 /* Flag indicating whether this module has been initialized. */
 105 static int initialized = 0;
 106
 107 /* Set to true if the connection is interactive. */
 108 static int interactive_mode = 0;
 109
 110 /* True if SSH2 packet format is used */
 111 int use_ssh2_packet_format = 0;
 112
 113 /* Session key information for Encryption and MAC */
 114 Kex     *kex = NULL;
 115
 116 void
 117 packet_set_kex(Kex *k)
 118 {
 119         if( k->mac[MODE_IN ].key == NULL ||
 120             k->enc[MODE_IN ].key == NULL ||
 121             k->enc[MODE_IN ].iv  == NULL ||
 122             k->mac[MODE_OUT].key == NULL ||
 123             k->enc[MODE_OUT].key == NULL ||
 124             k->enc[MODE_OUT].iv  == NULL)
 125                 fatal("bad KEX");
 126         kex = k;
 127 }
 128 void
 129 clear_enc_keys(Enc *enc, int len)
 130 {
 131         memset(enc->iv,  0, len);
 132         memset(enc->key, 0, len);
 133         xfree(enc->iv);
 134         xfree(enc->key);
 135         enc->iv = NULL;
 136         enc->key = NULL;
 137 }
 138 void
 139 packet_set_ssh2_format(void)
 140 {
 141         debug("use_ssh2_packet_format");
 142         use_ssh2_packet_format = 1;
 143 }
 144
 145 /*
 146  * Sets the descriptors used for communication.  Disables encryption until
 147  * packet_set_encryption_key is called.
 148  */
 149 void
 150 packet_set_connection(int fd_in, int fd_out)
 151 {
 152         connection_in = fd_in;
 153         connection_out = fd_out;
 154         cipher_type = SSH_CIPHER_NONE;
 155         cipher_set_key(&send_context, SSH_CIPHER_NONE, (unsigned char *) "", 0);
 156         cipher_set_key(&receive_context, SSH_CIPHER_NONE, (unsigned char *) "", 0);
 157         if (!initialized) {
 158                 initialized = 1;
 159                 buffer_init(&input);
 160                 buffer_init(&output);
 161                 buffer_init(&outgoing_packet);
 162                 buffer_init(&incoming_packet);
 163         }
 164         /* Kludge: arrange the close function to be called from fatal(). */
 165         fatal_add_cleanup((void (*) (void *)) packet_close, NULL);
 166 }
 167
 168 /* Returns 1 if remote host is connected via socket, 0 if not. */
 169
 170 int
 171 packet_connection_is_on_socket()
 172 {
 173         struct sockaddr_storage from, to;
 174         socklen_t fromlen, tolen;
 175
 176         /* filedescriptors in and out are the same, so it's a socket */
 177         if (connection_in == connection_out)
 178                 return 1;
 179         fromlen = sizeof(from);
 180         memset(&from, 0, sizeof(from));
 181         if (getpeername(connection_in, (struct sockaddr *)&from, &fromlen) < 0)
 182                 return 0;
 183         tolen = sizeof(to);
 184         memset(&to, 0, sizeof(to));
 185         if (getpeername(connection_out, (struct sockaddr *)&to, &tolen) < 0)
 186                 return 0;
 187         if (fromlen != tolen || memcmp(&from, &to, fromlen) != 0)
 188                 return 0;
 189         if (from.ss_family != AF_INET && from.ss_family != AF_INET6)
 190                 return 0;
 191         return 1;
 192 }
 193
 194 /* returns 1 if connection is via ipv4 */
 195
 196 int
 197 packet_connection_is_ipv4()
 198 {
 199         struct sockaddr_storage to;
 200         socklen_t tolen = sizeof(to);
 201
 202         memset(&to, 0, sizeof(to));
 203         if (getsockname(connection_out, (struct sockaddr *)&to, &tolen) < 0)
 204                 return 0;
 205         if (to.ss_family != AF_INET)
 206                 return 0;
 207         return 1;
 208 }
 209
 210 /* Sets the connection into non-blocking mode. */
 211
 212 void
 213 packet_set_nonblocking()
 214 {
 215         /* Set the socket into non-blocking mode. */
 216         if (fcntl(connection_in, F_SETFL, O_NONBLOCK) < 0)
 217                 error("fcntl O_NONBLOCK: %.100s", strerror(errno));
 218
 219         if (connection_out != connection_in) {
 220                 if (fcntl(connection_out, F_SETFL, O_NONBLOCK) < 0)
 221                         error("fcntl O_NONBLOCK: %.100s", strerror(errno));
 222         }
 223 }
 224
 225 /* Returns the socket used for reading. */
 226
 227 int
 228 packet_get_connection_in()
 229 {
 230         return connection_in;
 231 }
 232
 233 /* Returns the descriptor used for writing. */
 234
 235 int
 236 packet_get_connection_out()
 237 {
 238         return connection_out;
 239 }
 240
 241 /* Closes the connection and clears and frees internal data structures. */
 242
 243 void
 244 packet_close()
 245 {
 246         if (!initialized)
 247                 return;
 248         initialized = 0;
 249         if (connection_in == connection_out) {
 250                 shutdown(connection_out, SHUT_RDWR);
 251                 close(connection_out);
 252         } else {
 253                 close(connection_in);
 254                 close(connection_out);
 255         }
 256         buffer_free(&input);
 257         buffer_free(&output);
 258         buffer_free(&outgoing_packet);
 259         buffer_free(&incoming_packet);
 260         if (packet_compression) {
 261                 buffer_free(&compression_buffer);
 262                 buffer_compress_uninit();
 263         }
 264 }
 265
 266 /* Sets remote side protocol flags. */
 267
 268 void
 269 packet_set_protocol_flags(unsigned int protocol_flags)
 270 {
 271         remote_protocol_flags = protocol_flags;
 272         channel_set_options((protocol_flags & SSH_PROTOFLAG_HOST_IN_FWD_OPEN) != 0);
 273 }
 274
 275 /* Returns the remote protocol flags set earlier by the above function. */
 276
 277 unsigned int
 278 packet_get_protocol_flags()
 279 {
 280         return remote_protocol_flags;
 281 }
 282
 283 /*
 284  * Starts packet compression from the next packet on in both directions.
 285  * Level is compression level 1 (fastest) - 9 (slow, best) as in gzip.
 286  */
 287
 288 /*** XXXXX todo: kex means re-init */
 289 void
 290 packet_start_compression(int level)
 291 {
 292         if (packet_compression)
 293                 fatal("Compression already enabled.");
 294         packet_compression = 1;
 295         buffer_init(&compression_buffer);
 296         buffer_compress_init(level);
 297 }
 298
 299 /*
 300  * Encrypts the given number of bytes, copying from src to dest. bytes is
 301  * known to be a multiple of 8.
 302  */
 303
 304 void
 305 packet_encrypt(CipherContext * cc, void *dest, void *src,
 306     unsigned int bytes)
 307 {
 308         cipher_encrypt(cc, dest, src, bytes);
 309 }
 310
 311 /*
 312  * Decrypts the given number of bytes, copying from src to dest. bytes is
 313  * known to be a multiple of 8.
 314  */
 315
 316 void
 317 packet_decrypt(CipherContext * cc, void *dest, void *src,
 318     unsigned int bytes)
 319 {
 320         int i;
 321
 322         if ((bytes % 8) != 0)
 323                 fatal("packet_decrypt: bad ciphertext length %d", bytes);
 324
 325         /*
 326          * Cryptographic attack detector for ssh - Modifications for packet.c
 327          * (C)1998 CORE-SDI, Buenos Aires Argentina Ariel Futoransky(futo@core-sdi.com)
 328          */
 329
 330         if (cc->type == SSH_CIPHER_NONE || compat20) {
 331                 i = DEATTACK_OK;
 332         } else {
 333                 i = detect_attack(src, bytes, NULL);
 334         }
 335         if (i == DEATTACK_DETECTED)
 336                 packet_disconnect("crc32 compensation attack: network attack detected");
 337
 338         cipher_decrypt(cc, dest, src, bytes);
 339 }
 340
 341 /*
 342  * Causes any further packets to be encrypted using the given key.  The same
 343  * key is used for both sending and reception.  However, both directions are
 344  * encrypted independently of each other.
 345  */
 346
 347 void
 348 packet_set_encryption_key(const unsigned char *key, unsigned int keylen,
 349     int cipher)
 350 {
 351         if (keylen < 20)
 352                 fatal("keylen too small: %d", keylen);
 353
 354         /* All other ciphers use the same key in both directions for now. */
 355         cipher_set_key(&receive_context, cipher, key, keylen);
 356         cipher_set_key(&send_context, cipher, key, keylen);
 357 }
 358
 359 /* Starts constructing a packet to send. */
 360
 361 void
 362 packet_start1(int type)
 363 {
 364         char buf[9];
 365
 366         buffer_clear(&outgoing_packet);
 367         memset(buf, 0, 8);
 368         buf[8] = type;
 369         buffer_append(&outgoing_packet, buf, 9);
 370 }
 371
 372 void
 373 packet_start2(int type)
 374 {
 375         char buf[4+1+1];
 376
 377         buffer_clear(&outgoing_packet);
 378         memset(buf, 0, sizeof buf);
 379         /* buf[0..3] = payload_len; */
 380         /* buf[4] =    pad_len; */
 381         buf[5] = type & 0xff;
 382         buffer_append(&outgoing_packet, buf, sizeof buf);
 383 }
 384
 385 void
 386 packet_start(int type)
 387 {
 388         DBG(debug("packet_start[%d]",type));
 389         if (use_ssh2_packet_format)
 390                 packet_start2(type);
 391         else
 392                 packet_start1(type);
 393 }
 394
 395 /* Appends a character to the packet data. */
 396
 397 void
 398 packet_put_char(int value)
 399 {
 400         char ch = value;
 401         buffer_append(&outgoing_packet, &ch, 1);
 402 }
 403
 404 /* Appends an integer to the packet data. */
 405
 406 void
 407 packet_put_int(unsigned int value)
 408 {
 409         buffer_put_int(&outgoing_packet, value);
 410 }
 411
 412 /* Appends a string to packet data. */
 413
 414 void
 415 packet_put_string(const char *buf, unsigned int len)
 416 {
 417         buffer_put_string(&outgoing_packet, buf, len);
 418 }
 419 void
 420 packet_put_cstring(const char *str)
 421 {
 422         buffer_put_string(&outgoing_packet, str, strlen(str));
 423 }
 424
 425 void
 426 packet_put_raw(const char *buf, unsigned int len)
 427 {
 428         buffer_append(&outgoing_packet, buf, len);
 429 }
 430
 431
 432 /* Appends an arbitrary precision integer to packet data. */
 433
 434 void
 435 packet_put_bignum(BIGNUM * value)
 436 {
 437         buffer_put_bignum(&outgoing_packet, value);
 438 }
 439 void
 440 packet_put_bignum2(BIGNUM * value)
 441 {
 442         buffer_put_bignum2(&outgoing_packet, value);
 443 }
 444
 445 /*
 446  * Finalizes and sends the packet.  If the encryption key has been set,
 447  * encrypts the packet before sending.
 448  */
 449
 450 void
 451 packet_send1()
 452 {
 453         char buf[8], *cp;
 454         int i, padding, len;
 455         unsigned int checksum;
 456         u_int32_t rand = 0;
 457
 458         /*
 459          * If using packet compression, compress the payload of the outgoing
 460          * packet.
 461          */
 462         if (packet_compression) {
 463                 buffer_clear(&compression_buffer);
 464                 /* Skip padding. */
 465                 buffer_consume(&outgoing_packet, 8);
 466                 /* padding */
 467                 buffer_append(&compression_buffer, "\0\0\0\0\0\0\0\0", 8);
 468                 buffer_compress(&outgoing_packet, &compression_buffer);
 469                 buffer_clear(&outgoing_packet);
 470                 buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer),
 471                               buffer_len(&compression_buffer));
 472         }
 473         /* Compute packet length without padding (add checksum, remove padding). */
 474         len = buffer_len(&outgoing_packet) + 4 - 8;
 475
 476         /* Insert padding. */
 477         padding = 8 - len % 8;
 478         if (cipher_type != SSH_CIPHER_NONE) {
 479                 cp = buffer_ptr(&outgoing_packet);
 480                 for (i = 0; i < padding; i++) {
 481                         if (i % 4 == 0)
 482                                 rand = arc4random();
 483                         cp[7 - i] = rand & 0xff;
 484                         rand >>= 8;
 485                 }
 486         }
 487         buffer_consume(&outgoing_packet, 8 - padding);
 488
 489         /* Add check bytes. */
 490         checksum = crc32((unsigned char *) buffer_ptr(&outgoing_packet),
 491                          buffer_len(&outgoing_packet));
 492         PUT_32BIT(buf, checksum);
 493         buffer_append(&outgoing_packet, buf, 4);
 494
 495 #ifdef PACKET_DEBUG
 496         fprintf(stderr, "packet_send plain: ");
 497         buffer_dump(&outgoing_packet);
 498 #endif
 499
 500         /* Append to output. */
 501         PUT_32BIT(buf, len);
 502         buffer_append(&output, buf, 4);
 503         buffer_append_space(&output, &cp, buffer_len(&outgoing_packet));
 504         packet_encrypt(&send_context, cp, buffer_ptr(&outgoing_packet),
 505                        buffer_len(&outgoing_packet));
 506
 507 #ifdef PACKET_DEBUG
 508         fprintf(stderr, "encrypted: ");
 509         buffer_dump(&output);
 510 #endif
 511
 512         buffer_clear(&outgoing_packet);
 513
 514         /*
 515          * Note that the packet is now only buffered in output.  It won\'t be
 516          * actually sent until packet_write_wait or packet_write_poll is
 517          * called.
 518          */
 519 }
 520
 521 /*
 522  * Finalize packet in SSH2 format (compress, mac, encrypt, enqueue)
 523  */
 524 void
 525 packet_send2()
 526 {
 527         unsigned char *macbuf = NULL;
 528         char *cp;
 529         unsigned int packet_length = 0;
 530         unsigned int i, padlen, len;
 531         u_int32_t rand = 0;
 532         static unsigned int seqnr = 0;
 533         int type;
 534         Enc *enc   = NULL;
 535         Mac *mac   = NULL;
 536         Comp *comp = NULL;
 537         int block_size;
 538
 539         if (kex != NULL) {
 540                 enc  = &kex->enc[MODE_OUT];
 541                 mac  = &kex->mac[MODE_OUT];
 542                 comp = &kex->comp[MODE_OUT];
 543         }
 544         block_size = enc ? enc->block_size : 8;
 545
 546         cp = buffer_ptr(&outgoing_packet);
 547         type = cp[5] & 0xff;
 548
 549 #ifdef PACKET_DEBUG
 550         fprintf(stderr, "plain:     ");
 551         buffer_dump(&outgoing_packet);
 552 #endif
 553
 554         if (comp && comp->enabled) {
 555                 len = buffer_len(&outgoing_packet);
 556                 /* skip header, compress only payload */
 557                 buffer_consume(&outgoing_packet, 5);
 558                 buffer_clear(&compression_buffer);
 559                 buffer_compress(&outgoing_packet, &compression_buffer);
 560                 buffer_clear(&outgoing_packet);
 561                 buffer_append(&outgoing_packet, "\0\0\0\0\0", 5);
 562                 buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer),
 563                     buffer_len(&compression_buffer));
 564                 DBG(debug("compression: raw %d compressed %d", len,
 565                     buffer_len(&outgoing_packet)));
 566         }
 567
 568         /* sizeof (packet_len + pad_len + payload) */
 569         len = buffer_len(&outgoing_packet);
 570
 571         /*
 572          * calc size of padding, alloc space, get random data,
 573          * minimum padding is 4 bytes
 574          */
 575         padlen = block_size - (len % block_size);
 576         if (padlen < 4)
 577                 padlen += block_size;
 578         buffer_append_space(&outgoing_packet, &cp, padlen);
 579         if (enc && enc->type != SSH_CIPHER_NONE) {
 580                 for (i = 0; i < padlen; i++) {
 581                         if (i % 4 == 0)
 582                                 rand = arc4random();
 583                         cp[i] = rand & 0xff;
 584                         rand <<= 8;
 585                 }
 586         }
 587         /* packet_length includes payload, padding and padding length field */
 588         packet_length = buffer_len(&outgoing_packet) - 4;
 589         cp = buffer_ptr(&outgoing_packet);
 590         PUT_32BIT(cp, packet_length);
 591         cp[4] = padlen & 0xff;
 592         DBG(debug("send: len %d (includes padlen %d)", packet_length+4, padlen));
 593
 594         /* compute MAC over seqnr and packet(length fields, payload, padding) */
 595         if (mac && mac->enabled) {
 596                 macbuf = hmac( mac->md, seqnr,
 597                     (unsigned char *) buffer_ptr(&outgoing_packet),
 598                     buffer_len(&outgoing_packet),
 599                     mac->key, mac->key_len
 600                 );
 601                 DBG(debug("done calc HMAC out #%d", seqnr));
 602         }
 603         /* encrypt packet and append to output buffer. */
 604         buffer_append_space(&output, &cp, buffer_len(&outgoing_packet));
 605         packet_encrypt(&send_context, cp, buffer_ptr(&outgoing_packet),
 606             buffer_len(&outgoing_packet));
 607         /* append unencrypted MAC */
 608         if (mac && mac->enabled)
 609                 buffer_append(&output, (char *)macbuf, mac->mac_len);
 610 #ifdef PACKET_DEBUG
 611         fprintf(stderr, "encrypted: ");
 612         buffer_dump(&output);
 613 #endif
 614         /* increment sequence number for outgoing packets */
 615         if (++seqnr == 0)
 616                 log("outgoing seqnr wraps around");
 617         buffer_clear(&outgoing_packet);
 618
 619         if (type == SSH2_MSG_NEWKEYS) {
 620                 if (kex==NULL || mac==NULL || enc==NULL || comp==NULL)
 621                         fatal("packet_send2: no KEX");
 622                 if (mac->md != NULL)
 623                         mac->enabled = 1;
 624                 debug("cipher_set_key_iv send_context");
 625                 cipher_set_key_iv(&send_context, enc->type,
 626                     enc->key, enc->key_len,
 627                     enc->iv, enc->iv_len);
 628                 clear_enc_keys(enc, kex->we_need);
 629                 if (comp->type != 0 && comp->enabled == 0) {
 630                         comp->enabled = 1;
 631                         if (! packet_compression)
 632                                 packet_start_compression(6);
 633                 }
 634         }
 635 }
 636
 637 void
 638 packet_send()
 639 {
 640         if (use_ssh2_packet_format)
 641                 packet_send2();
 642         else
 643                 packet_send1();
 644         DBG(debug("packet_send done"));
 645 }
 646
 647 void
 648 packet_send_and_wait()
 649 {
 650         packet_send();
 651         packet_write_wait();
 652 }
 653
 654 /*
 655  * Waits until a packet has been received, and returns its type.  Note that
 656  * no other data is processed until this returns, so this function should not
 657  * be used during the interactive session.
 658  */
 659
 660 int
 661 packet_read(int *payload_len_ptr)
 662 {
 663         int type, len;
 664         fd_set set;
 665         char buf[8192];
 666         DBG(debug("packet_read()"));
 667
 668         /* Since we are blocking, ensure that all written packets have been sent. */
 669         packet_write_wait();
 670
 671         /* Stay in the loop until we have received a complete packet. */
 672         for (;;) {
 673                 /* Try to read a packet from the buffer. */
 674                 type = packet_read_poll(payload_len_ptr);
 675                 if (type == SSH_SMSG_SUCCESS
 676                     || type == SSH_SMSG_FAILURE
 677                     || type == SSH_CMSG_EOF
 678                     || type == SSH_CMSG_EXIT_CONFIRMATION)
 679                         packet_integrity_check(*payload_len_ptr, 0, type);
 680                 /* If we got a packet, return it. */
 681                 if (type != SSH_MSG_NONE)
 682                         return type;
 683                 /*
 684                  * Otherwise, wait for some data to arrive, add it to the
 685                  * buffer, and try again.
 686                  */
 687                 FD_ZERO(&set);
 688                 FD_SET(connection_in, &set);
 689
 690                 /* Wait for some data to arrive. */
 691                 select(connection_in + 1, &set, NULL, NULL, NULL);
 692
 693                 /* Read data from the socket. */
 694                 len = read(connection_in, buf, sizeof(buf));
 695                 if (len == 0) {
 696                         log("Connection closed by %.200s", get_remote_ipaddr());
 697                         fatal_cleanup();
 698                 }
 699                 if (len < 0)
 700                         fatal("Read from socket failed: %.100s", strerror(errno));
 701                 /* Append it to the buffer. */
 702                 packet_process_incoming(buf, len);
 703         }
 704         /* NOTREACHED */
 705 }
 706
 707 /*
 708  * Waits until a packet has been received, verifies that its type matches
 709  * that given, and gives a fatal error and exits if there is a mismatch.
 710  */
 711
 712 void
 713 packet_read_expect(int *payload_len_ptr, int expected_type)
 714 {
 715         int type;
 716
 717         type = packet_read(payload_len_ptr);
 718         if (type != expected_type)
 719                 packet_disconnect("Protocol error: expected packet type %d, got %d",
 720                     expected_type, type);
 721 }
 722
 723 /* Checks if a full packet is available in the data received so far via
 724  * packet_process_incoming.  If so, reads the packet; otherwise returns
 725  * SSH_MSG_NONE.  This does not wait for data from the connection.
 726  *
 727  * SSH_MSG_DISCONNECT is handled specially here.  Also,
 728  * SSH_MSG_IGNORE messages are skipped by this function and are never returned
 729  * to higher levels.
 730  *
 731  * The returned payload_len does include space consumed by:
 732  *      Packet length
 733  *      Padding
 734  *      Packet type
 735  *      Check bytes
 736  */
 737
 738 int
 739 packet_read_poll1(int *payload_len_ptr)
 740 {
 741         unsigned int len, padded_len;
 742         unsigned char *ucp;
 743         char buf[8], *cp;
 744         unsigned int checksum, stored_checksum;
 745
 746         /* Check if input size is less than minimum packet size. */
 747         if (buffer_len(&input) < 4 + 8)
 748                 return SSH_MSG_NONE;
 749         /* Get length of incoming packet. */
 750         ucp = (unsigned char *) buffer_ptr(&input);
 751         len = GET_32BIT(ucp);
 752         if (len < 1 + 2 + 2 || len > 256 * 1024)
 753                 packet_disconnect("Bad packet length %d.", len);
 754         padded_len = (len + 8) & ~7;
 755
 756         /* Check if the packet has been entirely received. */
 757         if (buffer_len(&input) < 4 + padded_len)
 758                 return SSH_MSG_NONE;
 759
 760         /* The entire packet is in buffer. */
 761
 762         /* Consume packet length. */
 763         buffer_consume(&input, 4);
 764
 765         /* Copy data to incoming_packet. */
 766         buffer_clear(&incoming_packet);
 767         buffer_append_space(&incoming_packet, &cp, padded_len);
 768         packet_decrypt(&receive_context, cp, buffer_ptr(&input), padded_len);
 769         buffer_consume(&input, padded_len);
 770
 771 #ifdef PACKET_DEBUG
 772         fprintf(stderr, "read_poll plain: ");
 773         buffer_dump(&incoming_packet);
 774 #endif
 775
 776         /* Compute packet checksum. */
 777         checksum = crc32((unsigned char *) buffer_ptr(&incoming_packet),
 778             buffer_len(&incoming_packet) - 4);
 779
 780         /* Skip padding. */
 781         buffer_consume(&incoming_packet, 8 - len % 8);
 782
 783         /* Test check bytes. */
 784
 785         if (len != buffer_len(&incoming_packet))
 786                 packet_disconnect("packet_read_poll: len %d != buffer_len %d.",
 787                     len, buffer_len(&incoming_packet));
 788
 789         ucp = (unsigned char *) buffer_ptr(&incoming_packet) + len - 4;
 790         stored_checksum = GET_32BIT(ucp);
 791         if (checksum != stored_checksum)
 792                 packet_disconnect("Corrupted check bytes on input.");
 793         buffer_consume_end(&incoming_packet, 4);
 794
 795         /* If using packet compression, decompress the packet. */
 796         if (packet_compression) {
 797                 buffer_clear(&compression_buffer);
 798                 buffer_uncompress(&incoming_packet, &compression_buffer);
 799                 buffer_clear(&incoming_packet);
 800                 buffer_append(&incoming_packet, buffer_ptr(&compression_buffer),
 801                     buffer_len(&compression_buffer));
 802         }
 803         /* Get packet type. */
 804         buffer_get(&incoming_packet, &buf[0], 1);
 805
 806         /* Return length of payload (without type field). */
 807         *payload_len_ptr = buffer_len(&incoming_packet);
 808
 809         /* Return type. */
 810         return (unsigned char) buf[0];
 811 }
 812
 813 int
 814 packet_read_poll2(int *payload_len_ptr)
 815 {
 816         unsigned int padlen, need;
 817         unsigned char buf[8], *macbuf;
 818         unsigned char *ucp;
 819         char *cp;
 820         static unsigned int packet_length = 0;
 821         static unsigned int seqnr = 0;
 822         int type;
 823         int maclen, block_size;
 824         Enc *enc   = NULL;
 825         Mac *mac   = NULL;
 826         Comp *comp = NULL;
 827
 828         if (kex != NULL) {
 829                 enc  = &kex->enc[MODE_IN];
 830                 mac  = &kex->mac[MODE_IN];
 831                 comp = &kex->comp[MODE_IN];
 832         }
 833         maclen = mac && mac->enabled ? mac->mac_len : 0;
 834         block_size = enc ? enc->block_size : 8;
 835
 836         if (packet_length == 0) {
 837                 /*
 838                  * check if input size is less than the cipher block size,
 839                  * decrypt first block and extract length of incoming packet
 840                  */
 841                 if (buffer_len(&input) < block_size)
 842                         return SSH_MSG_NONE;
 843                 buffer_clear(&incoming_packet);
 844                 buffer_append_space(&incoming_packet, &cp, block_size);
 845                 packet_decrypt(&receive_context, cp, buffer_ptr(&input),
 846                     block_size);
 847                 ucp = (unsigned char *) buffer_ptr(&incoming_packet);
 848                 packet_length = GET_32BIT(ucp);
 849                 if (packet_length < 1 + 4 || packet_length > 256 * 1024) {
 850                         buffer_dump(&incoming_packet);
 851                         packet_disconnect("Bad packet length %d.", packet_length);
 852                 }
 853                 DBG(debug("input: packet len %d", packet_length+4));
 854                 buffer_consume(&input, block_size);
 855         }
 856         /* we have a partial packet of block_size bytes */
 857         need = 4 + packet_length - block_size;
 858         DBG(debug("partial packet %d, need %d, maclen %d", block_size,
 859             need, maclen));
 860         if (need % block_size != 0)
 861                 fatal("padding error: need %d block %d mod %d",
 862                     need, block_size, need % block_size);
 863         /*
 864          * check if the entire packet has been received and
 865          * decrypt into incoming_packet
 866          */
 867         if (buffer_len(&input) < need + maclen)
 868                 return SSH_MSG_NONE;
 869 #ifdef PACKET_DEBUG
 870         fprintf(stderr, "read_poll enc/full: ");
 871         buffer_dump(&input);
 872 #endif
 873         buffer_append_space(&incoming_packet, &cp, need);
 874         packet_decrypt(&receive_context, cp, buffer_ptr(&input), need);
 875         buffer_consume(&input, need);
 876         /*
 877          * compute MAC over seqnr and packet,
 878          * increment sequence number for incoming packet
 879          */
 880         if (mac && mac->enabled) {
 881                 macbuf = hmac( mac->md, seqnr,
 882                     (unsigned char *) buffer_ptr(&incoming_packet),
 883                     buffer_len(&incoming_packet),
 884                     mac->key, mac->key_len
 885                 );
 886                 if (memcmp(macbuf, buffer_ptr(&input), mac->mac_len) != 0)
 887                         packet_disconnect("Corrupted HMAC on input.");
 888                 DBG(debug("HMAC #%d ok", seqnr));
 889                 buffer_consume(&input, mac->mac_len);
 890         }
 891         if (++seqnr == 0)
 892                 log("incoming seqnr wraps around");
 893
 894         /* get padlen */
 895         cp = buffer_ptr(&incoming_packet) + 4;
 896         padlen = *cp & 0xff;
 897         DBG(debug("input: padlen %d", padlen));
 898         if (padlen < 4)
 899                 packet_disconnect("Corrupted padlen %d on input.", padlen);
 900
 901         /* skip packet size + padlen, discard padding */
 902         buffer_consume(&incoming_packet, 4 + 1);
 903         buffer_consume_end(&incoming_packet, padlen);
 904
 905         DBG(debug("input: len before de-compress %d", buffer_len(&incoming_packet)));
 906         if (comp && comp->enabled) {
 907                 buffer_clear(&compression_buffer);
 908                 buffer_uncompress(&incoming_packet, &compression_buffer);
 909                 buffer_clear(&incoming_packet);
 910                 buffer_append(&incoming_packet, buffer_ptr(&compression_buffer),
 911                     buffer_len(&compression_buffer));
 912                 DBG(debug("input: len after de-compress %d", buffer_len(&incoming_packet)));
 913         }
 914         /*
 915          * get packet type, implies consume.
 916          * return length of payload (without type field)
 917          */
 918         buffer_get(&incoming_packet, (char *)&buf[0], 1);
 919         *payload_len_ptr = buffer_len(&incoming_packet);
 920
 921         /* reset for next packet */
 922         packet_length = 0;
 923
 924         /* extract packet type */
 925         type = (unsigned char)buf[0];
 926
 927         if (type == SSH2_MSG_NEWKEYS) {
 928                 if (kex==NULL || mac==NULL || enc==NULL || comp==NULL)
 929                         fatal("packet_read_poll2: no KEX");
 930                 if (mac->md != NULL)
 931                         mac->enabled = 1;
 932                 debug("cipher_set_key_iv receive_context");
 933                 cipher_set_key_iv(&receive_context, enc->type,
 934                     enc->key, enc->key_len,
 935                     enc->iv, enc->iv_len);
 936                 clear_enc_keys(enc, kex->we_need);
 937                 if (comp->type != 0 && comp->enabled == 0) {
 938                         comp->enabled = 1;
 939                         if (! packet_compression)
 940                                 packet_start_compression(6);
 941                 }
 942         }
 943
 944 #ifdef PACKET_DEBUG
 945         fprintf(stderr, "read/plain[%d]:\r\n",type);
 946         buffer_dump(&incoming_packet);
 947 #endif
 948         return (unsigned char)type;
 949 }
 950
 951 int
 952 packet_read_poll(int *payload_len_ptr)
 953 {
 954         char *msg;
 955         for (;;) {
 956                 int type = use_ssh2_packet_format ?
 957                     packet_read_poll2(payload_len_ptr):
 958                     packet_read_poll1(payload_len_ptr);
 959
 960                 if(compat20) {
 961                         int reason;
 962                         if (type != 0)
 963                                 DBG(debug("received packet type %d", type));
 964                         switch(type) {
 965                         case SSH2_MSG_IGNORE:
 966                                 break;
 967                         case SSH2_MSG_DEBUG:
 968                                 packet_get_char();
 969                                 msg = packet_get_string(NULL);
 970                                 debug("Remote: %.900s", msg);
 971                                 xfree(msg);
 972                                 msg = packet_get_string(NULL);
 973                                 xfree(msg);
 974                                 break;
 975                         case SSH2_MSG_DISCONNECT:
 976                                 reason = packet_get_int();
 977                                 msg = packet_get_string(NULL);
 978                                 log("Received disconnect: %d: %.900s", reason, msg);
 979                                 xfree(msg);
 980                                 fatal_cleanup();
 981                                 break;
 982                         default:
 983                                 return type;
 984                                 break;
 985                         }
 986                 } else {
 987                         switch(type) {
 988                         case SSH_MSG_IGNORE:
 989                                 break;
 990                         case SSH_MSG_DEBUG:
 991                                 msg = packet_get_string(NULL);
 992                                 debug("Remote: %.900s", msg);
 993                                 xfree(msg);
 994                                 break;
 995                         case SSH_MSG_DISCONNECT:
 996                                 msg = packet_get_string(NULL);
 997                                 log("Received disconnect: %.900s", msg);
 998                                 fatal_cleanup();
 999                                 xfree(msg);
1000                                 break;
1001                         default:
1002                                 if (type != 0)
1003                                         DBG(debug("received packet type %d", type));
1004                                 return type;
1005                                 break;
1006                         }
1007                 }
1008         }
1009 }
1010
1011 /*
1012  * Buffers the given amount of input characters.  This is intended to be used
1013  * together with packet_read_poll.
1014  */
1015
1016 void
1017 packet_process_incoming(const char *buf, unsigned int len)
1018 {
1019         buffer_append(&input, buf, len);
1020 }
1021
1022 /* Returns a character from the packet. */
1023
1024 unsigned int
1025 packet_get_char()
1026 {
1027         char ch;
1028         buffer_get(&incoming_packet, &ch, 1);
1029         return (unsigned char) ch;
1030 }
1031
1032 /* Returns an integer from the packet data. */
1033
1034 unsigned int
1035 packet_get_int()
1036 {
1037         return buffer_get_int(&incoming_packet);
1038 }
1039
1040 /*
1041  * Returns an arbitrary precision integer from the packet data.  The integer
1042  * must have been initialized before this call.
1043  */
1044
1045 void
1046 packet_get_bignum(BIGNUM * value, int *length_ptr)
1047 {
1048         *length_ptr = buffer_get_bignum(&incoming_packet, value);
1049 }
1050
1051 void
1052 packet_get_bignum2(BIGNUM * value, int *length_ptr)
1053 {
1054         *length_ptr = buffer_get_bignum2(&incoming_packet, value);
1055 }
1056
1057 char *
1058 packet_get_raw(int *length_ptr)
1059 {
1060         int bytes = buffer_len(&incoming_packet);
1061         if (length_ptr != NULL)
1062                 *length_ptr = bytes;
1063         return buffer_ptr(&incoming_packet);
1064 }
1065
1066 /*
1067  * Returns a string from the packet data.  The string is allocated using
1068  * xmalloc; it is the responsibility of the calling program to free it when
1069  * no longer needed.  The length_ptr argument may be NULL, or point to an
1070  * integer into which the length of the string is stored.
1071  */
1072
1073 char *
1074 packet_get_string(unsigned int *length_ptr)
1075 {
1076         return buffer_get_string(&incoming_packet, length_ptr);
1077 }
1078
1079 /*
1080  * Sends a diagnostic message from the server to the client.  This message
1081  * can be sent at any time (but not while constructing another message). The
1082  * message is printed immediately, but only if the client is being executed
1083  * in verbose mode.  These messages are primarily intended to ease debugging
1084  * authentication problems.   The length of the formatted message must not
1085  * exceed 1024 bytes.  This will automatically call packet_write_wait.
1086  */
1087
1088 void
1089 packet_send_debug(const char *fmt,...)
1090 {
1091         char buf[1024];
1092         va_list args;
1093
1094         va_start(args, fmt);
1095         vsnprintf(buf, sizeof(buf), fmt, args);
1096         va_end(args);
1097
1098         packet_start(SSH_MSG_DEBUG);
1099         packet_put_string(buf, strlen(buf));
1100         packet_send();
1101         packet_write_wait();
1102 }
1103
1104 /*
1105  * Logs the error plus constructs and sends a disconnect packet, closes the
1106  * connection, and exits.  This function never returns. The error message
1107  * should not contain a newline.  The length of the formatted message must
1108  * not exceed 1024 bytes.
1109  */
1110
1111 void
1112 packet_disconnect(const char *fmt,...)
1113 {
1114         char buf[1024];
1115         va_list args;
1116         static int disconnecting = 0;
1117         if (disconnecting)      /* Guard against recursive invocations. */
1118                 fatal("packet_disconnect called recursively.");
1119         disconnecting = 1;
1120
1121         /*
1122          * Format the message.  Note that the caller must make sure the
1123          * message is of limited size.
1124          */
1125         va_start(args, fmt);
1126         vsnprintf(buf, sizeof(buf), fmt, args);
1127         va_end(args);
1128
1129         /* Send the disconnect message to the other side, and wait for it to get sent. */
1130         if (compat20) {
1131                 packet_start(SSH2_MSG_DISCONNECT);
1132                 packet_put_int(SSH2_DISCONNECT_PROTOCOL_ERROR);
1133                 packet_put_cstring(buf);
1134                 packet_put_cstring("");
1135         } else {
1136                 packet_start(SSH_MSG_DISCONNECT);
1137                 packet_put_string(buf, strlen(buf));
1138         }
1139         packet_send();
1140         packet_write_wait();
1141
1142         /* Stop listening for connections. */
1143         channel_stop_listening();
1144
1145         /* Close the connection. */
1146         packet_close();
1147
1148         /* Display the error locally and exit. */
1149         log("Disconnecting: %.100s", buf);
1150         fatal_cleanup();
1151 }
1152
1153 /* Checks if there is any buffered output, and tries to write some of the output. */
1154
1155 void
1156 packet_write_poll()
1157 {
1158         int len = buffer_len(&output);
1159         if (len > 0) {
1160                 len = write(connection_out, buffer_ptr(&output), len);
1161                 if (len <= 0) {
1162                         if (errno == EAGAIN)
1163                                 return;
1164                         else
1165                                 fatal("Write failed: %.100s", strerror(errno));
1166                 }
1167                 buffer_consume(&output, len);
1168         }
1169 }
1170
1171 /*
1172  * Calls packet_write_poll repeatedly until all pending output data has been
1173  * written.
1174  */
1175
1176 void
1177 packet_write_wait()
1178 {
1179         packet_write_poll();
1180         while (packet_have_data_to_write()) {
1181                 fd_set set;
1182                 FD_ZERO(&set);
1183                 FD_SET(connection_out, &set);
1184                 select(connection_out + 1, NULL, &set, NULL, NULL);
1185                 packet_write_poll();
1186         }
1187 }
1188
1189 /* Returns true if there is buffered data to write to the connection. */
1190
1191 int
1192 packet_have_data_to_write()
1193 {
1194         return buffer_len(&output) != 0;
1195 }
1196
1197 /* Returns true if there is not too much data to write to the connection. */
1198
1199 int
1200 packet_not_very_much_data_to_write()
1201 {
1202         if (interactive_mode)
1203                 return buffer_len(&output) < 16384;
1204         else
1205                 return buffer_len(&output) < 128 * 1024;
1206 }
1207
1208 /* Informs that the current session is interactive.  Sets IP flags for that. */
1209
1210 void
1211 packet_set_interactive(int interactive, int keepalives)
1212 {
1213         int on = 1;
1214
1215         /* Record that we are in interactive mode. */
1216         interactive_mode = interactive;
1217
1218         /* Only set socket options if using a socket.  */
1219         if (!packet_connection_is_on_socket())
1220                 return;
1221         if (keepalives) {
1222                 /* Set keepalives if requested. */
1223                 if (setsockopt(connection_in, SOL_SOCKET, SO_KEEPALIVE, (void *) &on,
1224                     sizeof(on)) < 0)
1225                         error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1226         }
1227         /*
1228          * IPTOS_LOWDELAY, TCP_NODELAY and IPTOS_THROUGHPUT are IPv4 only
1229          */
1230         if (!packet_connection_is_ipv4())
1231                 return;
1232         if (interactive) {
1233                 /*
1234                  * Set IP options for an interactive connection.  Use
1235                  * IPTOS_LOWDELAY and TCP_NODELAY.
1236                  */
1237                 int lowdelay = IPTOS_LOWDELAY;
1238                 if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, (void *) &lowdelay,
1239                     sizeof(lowdelay)) < 0)
1240                         error("setsockopt IPTOS_LOWDELAY: %.100s", strerror(errno));
1241                 if (setsockopt(connection_in, IPPROTO_TCP, TCP_NODELAY, (void *) &on,
1242                     sizeof(on)) < 0)
1243                         error("setsockopt TCP_NODELAY: %.100s", strerror(errno));
1244         } else {
1245                 /*
1246                  * Set IP options for a non-interactive connection.  Use
1247                  * IPTOS_THROUGHPUT.
1248                  */
1249                 int throughput = IPTOS_THROUGHPUT;
1250                 if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, (void *) &throughput,
1251                     sizeof(throughput)) < 0)
1252                         error("setsockopt IPTOS_THROUGHPUT: %.100s", strerror(errno));
1253         }
1254 }
1255
1256 /* Returns true if the current connection is interactive. */
1257
1258 int
1259 packet_is_interactive()
1260 {
1261         return interactive_mode;
1262 }
1263
1264 int
1265 packet_set_maxsize(int s)
1266 {
1267         static int called = 0;
1268         if (called) {
1269                 log("packet_set_maxsize: called twice: old %d new %d",
1270                     max_packet_size, s);
1271                 return -1;
1272         }
1273         if (s < 4 * 1024 || s > 1024 * 1024) {
1274                 log("packet_set_maxsize: bad size %d", s);
1275                 return -1;
1276         }
1277         log("packet_set_maxsize: setting to %d", s);
1278         max_packet_size = s;
1279         return s;
1280 }